The present invention relates to methods for treating a subterranean formation. More particularly, the present invention relates to the use of vibrational waves in combination with a consolidating agent in remedial treatments of a subterranean formation.
In a typical subterranean well, damage to the surrounding formation can impede fluid flow and may cause production levels to drop. While many damage mechanisms plague wells, one of the most pervasive problems is fines clogging formation pores that usually allow hydrocarbon flow. As used herein, the term “fines” refers to loose particles, such as formation fines, formation sand, clay particulates, coal fines, resin particulates, crushed proppant or gravel particulates, and the like. These fines can also obstruct fluid flow pathways in screens; preslotted, predrilled, or cemented and perforated liners; and gravel packs that may line a well. Fines may even restrict fluid flow in openhole wells. For example, in situ fines mobilized during production can lodge themselves in formation pores, preslotted liners, screens, and gravel packs, preventing or reducing fluid flow there through.
Well-stimulation techniques have been developed to at least mitigate the problems caused by fines. One such technique is matrix acidizing. In matrix acidizing, pumps may inject thousands of gallons of acid into the well to dissolve away precipitates, fines, or scale on the inside of tubulars, in the pores of a screen or gravel pack, or inside the formation. Any tool, screen, liner, or casing that comes into contact with the acid should be protected from its corrosive effects. A corrosion inhibitor generally is used to prevent tubulars from corrosion. Also, the acid must be removed from the well. Often, the well must also be flushed with pre- and post-acid solutions. Aside from the difficulties of determining the proper chemical composition for these fluids and pumping them down the well, the environmental costs of matrix acidizing can render the process undesirable. Additionally, maxtrix acidizing treatments generally only provide a temporary solution to these problems. Screens, preslotted liners, and gravel packs may also be flushed with a brine solution to remove solid particles. While this brine treatment is cheap and relatively easy to complete, it offers only a temporary and localized respite from the plugging fines. Moreover, frequent flushing can damage the formation and further decrease production.
Acoustic stimulation is another technique that has been developed as an alternative to address these problems. In acoustic stimulation used for near-borehole cleaning, vibrational waves transfer vibrational energy to the fines clogging formation pores. In some instances, these vibrational waves may be generated using a pulsonic device, such as a fluidic oscillator. The ensuing vibration of the fines displace them from the pores, thereby allowing increased fluid flow there through. Fluid flow, including production-fluid flow out of the formation or injection-fluid flow into the formation from the well, may cause the particles to migrate out of the pores, clearing the way for greater fluid flow. Acoustic stimulation may also be used to clean preslotted liners, screens, and gravel packs.